In the past many injuries have occurred in industry when workmen have been in hazardous positions relative to machinery at the time of start-up of the machinery, the workmen subsequently being injured due to the initial start-up of the machinery. For example, a workman may be standing on a conveyor when the conveyor is started, the initial movement of the conveyor causing the workman to be thrown off balance and subsequently injured. In order to prevent such accidents from happening the operation of the machinery, when possible, will normally observe the machinery before start-up to make sure that no workmen are in hazardous positions. While this procedure will minimize injuries, if followed, in some occasions the operator of the machinery will fail to check to see that no one is endangered when the machinery is started. On other occasions, due to the location of the starting switch, it is not possible to see all locations of the machinery to see if it is safe to start the machinery. Therefore, it has been previously proposed to incorporate alarm circuits within the starting circuits of such machinery. The alarm circuits may include either an audible alarm, such as an electrically driven horn or buzzer, or may include lights, or both. Such alarm systems are now in many cases required by the Occupational Safety and Health Act. Heretofore, when adding alarm circuits to existing machinery it has been necessary to substantially rewire the existing machinery putting in suitable time delay circuits and alarm devices, the installation of such alarm devices not only causing the person responsible for making such changes the necessity of designing the various circuits and the bother of purchasing the various components, but also causing substantial down time on the machinery while such warning circuits and delayed starting circuits are added.